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    Enantiomeric recognition of amino acid ester salts by ?-cyclodextrin derivatives: an experimental and computational study
    (Arkat Usa Inc, 2016) Rezanka, Michal; Stibor, Ivan; Azizoglu, Murat; Turgut, Yilmaz; Pirinccioglu, Necmettin
    beta-cyclodextrin derivatives bearing benzoyl (beta-CD-1) and naphthoyl beta-CD-2) moieties have been synthesized from salicylic acid and 3-hydroxy-2-naphthoic acid by a convenient method in 60% and 58% yields, respectively, and were tested for enantiomeric recognition of amino acid ester derivatives. Their ability to discriminate between various L-/D-amino acid methyl ester hydrochloride salts was examined using the H-1 NMR titration method in DMSO-d(6) at 25 degrees C. beta-CD- 2 produced a fairly good discrimination of tryptophan ester salts with a binding constant of 4041 M-1 for L-salt compared with 2864 M-1 for D-salt, which corresponds to a difference of 0.21 kcal mol(-1) in binding free energies. The binding free energies obtained from molecular dynamic calculation by MM/PB(GB) SA are consistent with those obtained from the experimental results.
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    ?-Hydroxyamide derivatives of salicylic acid as organocatalysts for enantioselective reductions of prochiral ketones
    (Pergamon-Elsevier Science Ltd, 2013) Turgut, Yilmaz; Azizoglu, Murat; Erdogan, Asli; Arslan, Nevin; Hosgoren, Halil
    In order to find the most effective catalyst for the enantioselective reduction of a prochiral ketone, a series of novel beta-hydroxyamide derivatives of salicylic acid and chiral amino alcohols were synthesized. Different substituted prochiral ketones have been reduced in high yield (up to 99%) and the corresponding secondary alcohols are formed with good enantiomeric excess (up to 86%). The mechanism of this type of catalyst can be explained by considering the reaction mechanism for the CBS catalyst. (C) 2013 Elsevier Ltd. All rights reserved.
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    A series of novel ?-hydroxyamide based catalysts for borane-mediated enantioselective reductions of prochiral ketones
    (Pergamon-Elsevier Science Ltd, 2016) Azizoglu, Murat; Erdogan, Asli; Arslan, Nevin; Turgut, Yilmaz; Hosgoren, Halil; Pirinccioglu, Necmettin
    The enantioselective reduction of prochiral ketones with borane in the presence of a chiral ligand has received considerable attention. Hydroxylamine-based chiral ligands with amide and hydroxyl functions in the presence of other co-ordinating groups are highly effective in these asymmetric reductions. The current work presents a simple one step synthesis of a series of beta-hydroxyamide-based ligands from the reaction between 3-hydroxy-2-naphthoic acid and chiral amino alcohols and their applications as catalysts in asymmetric borane-mediated reductions of aromatic prochiral ketones in THE The reductions provided the corresponding secondary alcohols with up to 96% ee and in good to excellent yields (89-99%). OFF calculations at B3LYP/6-31+g(d) level offered theoretical models to account for the enantioselectivity imposed by the chiral ligands in the reductions of the ketones. (C) 2016 Elsevier Ltd. All rights reserved.